1. Field of the Invention
The present invention relates to a print head of a dot-printer for printing letters on paper on a platen and more particularly to mechanism for adjusting print wire point ends which are slidably mounted on a nose and project from a wire point guide.
2. Description of the Prior Art
A conventional print head generally comprises a nose having plurality of print wires, solenoid bases having a plurality of cores which are arranged annularly or ovally and each of which have a solenoid bobbin, and an armature base having a plurality of armatures reciprocatably mounted thereon. An armature spring for supporting the fulcrum of each armature is mounted between the armature and the armature base.
Such a conventional print head is mounted by mounting the nose of the print head on a carriage which is slidable along a carriage rail which is mounted parallel to a platen.
The performance of the print head is affected by the length of the print wires projecting from the wire point guide mounted on the nose and the distance between the wire point ends and the platen. If the print wire point ends project too much from the wire point guide, the print wires catch in the ink ribbon.
If the print wire point ends do not project enough, the printing action is not sufficiently strong because the amount of movement of the wire is fixed.
If the distance between the wire point ends and the platen is too great, the printing becomes too light. If the distance between the wire point ends and the platen is too small, movement of the printed paper is prevented or the paper is torn.
Conventionally, distance between the wire point ends and the platen is adjusted by adjusting the position of the platen and the carriage rail relative to each other. For example, both ends of the carriage rail have an eccentric cam thereon and an adjusting lever is mounted on the eccentric cam for carrying out this adjustment.
Conventionally, the distance the print wires project from the wire point guide is adjusted by inserting spacers having various thicknesses between the nose and the solenoid base.
However, it is difficult to provide space for inserting the spaces because the mechanism overlaps the position of a flexible print circuit. Since the nose is mounted on the carriage, the distance between the wire point ends and the platen is altered by the amount of the clearance between the base portion of the carriage on which the nose is mounted and the wire point ends.
Therefore, the said distance must be adjusted every time the print head is exchanged. This distance adjustment requires a great deal of skill.
Generally, the adjustment made at the time of an exchange of the print head must be dealt with by the end user of the printer.
It is difficult for the printer user to adjust the wire points to the most preferable position, and it is also very troublesome.
A conventional print head has a heat sink which is fixed to a solenoid base and armature base by adhesive. It is difficult to disassemble and assemble. Such a print head is fixed directly to the carriage by means of the nose. Heat from the heat sink is radiated only to the atmosphere.